1. Field of the Invention
The present invention relates to an endoscope apparatus that performs image pickup using an image pickup device including a color mosaic filter.
2. Description of the Related Art
An endoscope including an image pickup device at a distal end portion of an insertion portion is widely used in a medical field and an industrial field.
In recent years, according to an increase in the number of pixels of an image pickup device, an image pickup device for color provided with a color filter in an image pickup device has a merit that color image pickup can be performed under white illumination and problems of color drift and a decrease in a frame rate can be further avoided than an image pickup device for monochrome in which a color filter requiring frame sequential illumination is not provided.
On the other hand, besides being used in an application for performing a normal endoscopy under illumination of white light, there is also a need for performing an endoscopy under special illumination light.
For example, a conventional example of Japanese Patent Application Laid-Open Publication No. 2010-184047 discloses an endoscope apparatus that performs a normal observation by normal illumination light and a special light observation by special light illumination using a charge coupled device (abbreviated as CCD) including color filters of R, G, and B.
When a simultaneous photographing mode is selected, a light source for normal illumination light and a light source for special illumination light alternately or simultaneously irradiate the normal illumination light and the special illumination light in accumulation period units of the CCD. The CCD in an inter-line transfer type immediately starts, in a 2n-th image pickup operation, charge accumulation in a light-receiving element after reading out and transferring a signal charge to a vertical CCD from the light-receiving element in a 2n−1-th image pickup operation. After the charge accumulation, the CCD performs readout and transfer according to a readout pulse. After the readout and transfer, the CCD retains the signal charge in the vertical CCD until horizontal transfer of the signal charge by the 2n−1-th image pickup operation ends.